Sub-band coder design incorporating quadrature filters and pitch prediction

In this paper we discuss several new issues in the design of sub-band coders for low bit-rate speech coding. We use unequally spaced filter banks to match perceptual criteria for speech. In particular, we apply quadrature mirror filter techniques to provide cancellation of aliasing between sub-bands, thus permitting a reduction in the order of the filters. Preliminary investigations have been made into the use of pitch prediction within the sub-bands. Designs will be discussed for coder bit rates of 9.6 and 16 kb/s and their performance will be compared with earlier sub-band coder designs.